Oral care compositions, including toothpaste compositions, can contain fluoride salts, abrasives, and flavors to clean teeth, freshen breath, and maintain the aesthetics and health of the oral cavity, including the teeth and gums. It can also be desirable to include potassium nitrate (KNO3) in oral care compositions to help reduce pain from sensitive teeth (dentinal hypersensitivity) and a peroxide, like hydrogen peroxide, to help whiten teeth.
However, formulating toothpaste compositions with the proper stability and rheology can be very challenging, especially when the composition contains peroxide and potassium nitrate. First, alkali metal salts, like potassium nitrate, catalyze the hydrolysis of peroxide. When peroxide breaks down, it forms oxygen, water, and radicals. The excess gas can cause swelling and bursting of primary packaging and the radicals can cause the entire oral care composition, including the actives and flavors, to break down to a composition with a water like viscosity with decreased efficacy. Furthermore, unacceptable phase separation has been observed in certain toothpastes that KNO3.
As such, there is a need for an improved oral care composition that is stable, has acceptable rheology, and contains peroxide and potassium nitrate.